Soil Fumigation. December 2006

Transcription

1 Soil Fumigation December 2006 A study guide for persons seeking certification by the State of Hawaii Department of Agriculture to buy, use, or supervise the use of soil fumigants classified as restricted use pesticides Prepared by the staff of the Pesticide Risk Reduction Education Program, Cooperative Extension Service, College of Tropical Agriculture and Human Resources, University of Hawaii at Manoa DEVELOPMENT OF THIS GUIDE WAS SUPPORTED IN PART BY THE STATE OF HAWAII DEPARTMENT OF AGRICULTURE. 1

2 This guide mainly consists of text and pictures adapted from the publication Soil Fumigation (SM-61, June 1997), O. Norman Nesheim, Thomas W. Dean, and Michael J. Aerts, Institute of Food and Agricultural Sciences, Cooperative Extension Service, University of Florida. Chapter 1 Importance of Fumigant Product Labeling was added. The section Hazardous Materials Management in Chapter 6 was significantly revised. Where trade names are used, no endorsement is intended, nor criticism implied of similar products not named. 2

3 Table of Contents Chapter 1: Importance of Fumigant Product Labeling Chapter 2: Soil Fumigation Learning Objectives... 7 Introduction... 7 Fumigant Formulations and Descriptions 7 Liquified gases Volatile liquids Solids Pests Controlled by Soil Fumigation... 8 Nematodes Soil Fungi Bacteria Insects Weeds Factors Influencing Soil Fumigation... 9 Pest habits Soil texture Soil condition Plant debris Soil misture Soil temperature Application depth Dosage Soil sealing Exposure period Soil aeration Phytotoxicity Test Your Knowledge Chapter 3: Application Principles Learning Objectives Application Techniques and Equipment 13 Liquefied Gas Above ground applications Injection applications Auger applications Volatile Liquids Trench applications Handgun applications Shank (chisel) applications Sweep or blade applications Drench applications Chemigation Volatile Solids Broadcast applications Test Your Knowledge Chapter 4: Equipment Calibration Learning Objectives Calibration Methods Application over a known area Useful conversions for calibration Calculate flow rate per unit time Practice Problems Test Your Knowledge Chapter 5: Soil Fumigant Uses and Characteristics Learning Objectives Methyl Bromide Chloropicrin Metam-sodium ,3-D (1,3-Dichloropro-pene, Telone ) 24 Dazomet Test Your Knowledge

4 Chapter 6: Fumigation Safety Learning Objectives Introduction Safety Precautions For Applicators Personal Protective Equipment Respiratory Protection for Fumigant Application Threshold Limit Values Fumigant Poisoning Recognizing Fumigant Poisoning Symptoms Methyl Bromide Chloropicrin Metam-sodium 1,3-D (1,3e-Dichloropropene, Telone ) Dazomet First Aid Personal Sanitation Other Safety Recommendations Good Practices To Follow When Fumigating Test Your Knowledge Chapter 7: Storing, Handling, and Disposing of Fumigants Learning Objectives Storage of Soil Fumigants Disposal Hazardous Materials Management Spill and Leak Clean-Up Procedures Test Your Knowledge Glossary

5 CHAPTER 1 Importance of Fumigant Product Labeling Parts of this study guide discuss instructions and restrictions for handling fumigant pesticides. These discussions are general in nature because details for using one fumigant product may be different from those for another. Therefore, refer to the labeling supplied with your fumigant product as you plan a fumigation job. Let the product s labeling be your guide to an effective and safe fumigation job. Review all of the labeling do s and don t s about storage, use, and disposal. Be sure you can comply with the those that apply to you. Some will require you to have additional supplies or equipment such as special respirators or gas detection equipment. Others will require you to post special signs around the fumigation site before the fumigant job begins. Illness, injury, or pollution resulting from imporper storage, use, or disposal or the fumigant product will be investigated and the fumigator may be held partly or entirely responsible if he or she did not comply with the labeling. To get help interpreting a complex instruction or restriction, consult the product manufacturer s representative, or talk to a pesticide education specialist at one of these the Hawaii Department of Agriculture offices: Honolulu or (for Kauai and Oahu) Kahului (for Maui, Molokai, and Lanai) Hilo (for Hawaii) 808 is the area code for all of these phone numbers. * * * 5

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7 CHAPTER 2 Soil Fumigation Learning Objectives After you complete your study of this chapter, you should be able to: Name and describe the three fumigant formulations. Name the pests controlled by soil fumigation. Describe soil characteristics that influence penetration and movement of fumigants. Describe the factors that influence fumigant placement. Know the importance of soil sealing in soil fumigation Introduction Soil fumigation is a chemical control strategy used independently or in conjunction with cultural and physical control methods to reduce populations of soil organisms. Soil fumigants can effectively control soil-borne organisms, such as nematodes, fungi, bacteria, insects, weed seeds, and weeds. Different fumigants have varying effects on the control of these pests. Some are pest-specific, while others are broad spectrum biocides and kill most soil organisms. Soil fumigants are used in agriculture, nurseries, ornamental plant beds, forest systems, and other areas where soil-borne pests can harm or devastate desirable plants. Because of treatment costs, applicators use soil fumigants primarily on high value crops, such as vegetables, fruits, and ornamentals. Control of soil-borne pests will improve plant appearance, quality and vigor, crop yields, and ultimately profitability. Soil fumigation uses pesticide formulations that volatilize from a liquid or solid into a gas state. Soil fumigants are applied to the soil as liquefied gases, volatile liquids, or granules. Due to the high volatility of these compounds, the fumigant must be incorporated into the soil during or immediately following application. At or shortly after application, these chemicals volatilize, allowing toxic molecules to move through the air pores in the soil. Some molecules dissolve in the water film surrounding the soil particles. Soil pests are killed when they come in contact with a toxic concentration for a long enough exposure period. Fumigant Formulations and Descriptions Liquefied gases are gaseous under normal temperatures and pressures. The gas is liquid when held in a pressurized container. When released from a container, the liquid immediately converts to gas. Volatile liquids are liquid under normal temperatures and pressures but converts into a gas when in the soil. Solids are granular under normal temperatures but volatilize into a gas when in the soil. Characteristics of Fumigants. Soon after fumigants are applied to the soil, they begin to diffuse through the soil; they move from zones of high concentration to zones of lower concentration. Also, fumigants are decomposed by soil microorganisms or by chemical actions within the soil. Eventually, their concentration in the soil becomes negligible because they diffuse into the atmosphere and they decompose within the soil. Since seeds and plants in fumigated soil would be harmed by even low concentrations of fumigant in the soil, growers must delay planting until the fumigant has sufficiently decomposed and diffused out of the soil. This preplant interval (aeration period) will vary with the fumigant, its rate of 7

8 application, and environmental conditions. Most soil fumigants are labeled for use only as preplant (before planting) treatments because treatments made at planting or soon after planting would be toxic to the seeds and transplants. Fumigation only controls those target pests present in the soil at the time of fumigation. Fumigants have no residual activity and will not control pests that infest the fumigated soil after the aeration period. Pests Controlled by Soil Fumigation Soil pests, such as plant-parasitic nematodes, fungi, insects, bacteria, weeds, and weed seeds, can be controlled effectively by proper soil fumigation. The label of each fumigant will state the pests it will control. Proper identification of a pest is crucial to the success of the fumigation process. Understanding the life cycles and habits of different pests helps determine the proper application timing to target the susceptible stage of the pest. Also, proper application depth can be determined to ensure adequate contact with the pest. For some pests, especially nematodes, a soil analysis is necessary for proper identification. The diagnosis of nematode injury based only on nonspecific foliar symptoms is usually quite difficult, if not impossible. The affected host must be carefully examined to eliminate other possible causes of decline. An accurate diagnosis of a nematode problem, however, can only be made on the basis of a soil analysis. For assistance in pest identification and taking soil samples for analysis, contact your county extension agent. Nematodes are tiny, transparent, unsegmented, round worms, varying in size from 1/300 to 1/3 inch long. Several thousand species are known, but only a few of these are plant parasites. Plant parasitic nematodes attack small, succulent feeder roots. Their needle-like mouthparts puncture plant cells and suck out the contents. They reproduce by laying eggs. Nematodes live either in the water film in and around soil particles and plant tissue, or within plant tissue. Ectoparasitic plant nematodes remain on the outside of the plant. Most ectoparasitic nematodes migrate freely over the root surface, while some species remain at one point to feed. Endoparasitic nematodes move into the plant tissues to feed. They may move in and out of roots or remain sedentary within the root. At certain life stages, endoparasitic nematodes are present in the soil. Soil Fungi. Fungi are plant-like organisms that lack chlorophyll. This means they must obtain nutrients from other living sources, such as plants, animals, or organic matter. Most fungi reproduce by spores. Fungal spores germinate into thread-like filaments called hyphae that grow, secrete enzymes, absorb nutrients, and release chemicals that induce plant diseases. Some soil fumigants are effective in controlling soil fungi. Bacteria. Some bacteria that cause plant diseases also live in the soil. Bacteria are small, onecelled organisms that reproduce by simple fission. They obtain nutrients from plant cells and generally infect plants by entering through a wounds or a plants natural openings. Insects. There are several insects and insect relatives that live in the soil and are pests of plants. The insects are generally immature stages of beetles and flies. These two groups of insects undergo complete metamorphosis, which means they go through four distinct stages of development from the egg to an adult. These stages are egg, larva, pupa, and adult. It is usually the larval stage that causes damage, though some adults will also feed on underground plant parts. Some soil fumigants are successful in controlling soil insects. Weeds are unwanted plants that compete with desirable plants for space, water, nutrients, and light. These pests increase maintenance costs and may act as alternate hosts for insects and diseases. Some fumigants control weed seeds and germinating weeds. 8

9 Factors Influencing Soil Fumigation Many factors affect soil fumigation and its effectiveness for pest control. The pest and its habits will affect fumigant selection, application rate, fumigant placement, and necessary length of exposure. Soil factors also play a key role in fumigation. Soil texture, soil condition, debris, soil moisture, and soil temperature may affect the volatility, movement, and availability of the fumigant once applied. Fumigant dosage is both pest- and soil-dependent. The following section discusses some of these factors in greater detail. After fumigation, aeration is important to make sure phytotoxicity does not occur. Pest habits. Proper identification of the pest(s) is crucial. Once you have properly identified the pest, you can find out about pest life cycles and habits. Understanding the pest s habits provides information for proper timing of fumigant application to target the susceptible stage of the pest and for proper application depth to ensure adequate contact with the pest organisms. (Contact your local Cooperative Extension agent for assistance in pest identification.) Soil texture influences fumigant movement and availability due to its effects on the amount of soil pore space (air spaces) and the number of Know Where the Pests Live adsorption (binding) sites. Fine textured soils, such as clay, have many adsorption sites per unit area and many pore spaces. Coarse-textured soils have relatively few binding sites and few air spaces. For these reasons, soils high in clay content require more fumigant to attain a lethal dose. Generally, coarsertextured soils require less fumigant than fine-textured soils. Organic matter in soil greatly increases soil holding capacity and number of binding sites; thus soils high in organic matter require more fumigant. Read the label for any statements regarding amount of clay content or organic matter in soils. Soil condition is a major factor in fumigant penetration and diffusion. Fumigants do not move uniformly through the soil. Compacted soil limits the amount of diffusion and penetration. Cultivation of soil prior to fumigation is essential. Cultivate the soil to the level where the fumigant needs to diffuse. Break up or remove soil lumps, clods, and undecomposed organic matter. Pulverize and smooth the soil surface before fumigation to aid post application sealing, if required. Sealing prevents fumigant vapor from escaping too quickly. Improper soil preparation is the major reason for fumigation failures. Fumigate soils before applying manure, sawdust, or other organic matter. Plant debris can pose problems to shank-type fumigation, if excessive amounts of fresh or decaying plant material are present. Organic matter binds with the fumigant, making it unavailable for free movement. If a high concentration of organic matter is near the soil surface, it may impede proper diffusion of the fumigant and it may create avenues (chimneys) for gas to escape. Work all vegetation into the soil thoroughly. Allow vegetation plenty of time to decompose before fumigation. Do not fumigate soils that contain excessive amounts of organic matter. Soil moisture affects the diffusion of the fumigant. Most fumigations are conducted when the soil reaches 50% 75% field capacity of moisture. Fumigation requires a certain amount of soil moisture to ensure that the fumigant does not escape too quickly. Though too much moisture may impede fumigant movement because soil pores filled with water do not allow the gas to move. Cold, wet soils 9

10 retard diffusion and require a longer than normal exposure period. The soil moisture requirements necessary for effective fumigation differ among fumigants; read the product label directions carefully. Soil temperature correlates directly with fumigant volatility and movement. Soil temperature determines the fumigant state (solid, liquid or gas). As temperatures increase, fumigant volatility and diffusion increase. Generally, soil temperatures of F at the depth of fumigant injection are best for volatilization. Temperatures below the label minimum reduce volatilization and penetration, and the fumigant persists longer in the soil profile. Temperatures above the label maximum increase fumigant volatilization and soil penetration to the point where it breaks down or is lost from the soil before it reaches a level that is toxic to the target pest(s). The effect of soil temperature differs among fumigants; some are active at 40 F, while others remain in the nongaseous state at that temperature. Application depth is variable. Proper fumigant placement depends on a combination of factors, including where the pest organism lives, soil temperature, dosage, vapor pressure, and soil type. If the application is deep, the rate is too low, and the pest organisms are relatively shallow, the fumigant may not diffuse far enough upward to contact the pest at a sufficient dose (concentration, in ppm time, in hours) to obtain control. If the application is too shallow, the fumigant may not diffuse far enough downward to reach the pests. The fumigant may actually dissipate upward and out of the soil. Split depth applications may be necessary if soil condition is marginal and if broad depth control is required. For example, the fumigant may need to be placed at depths of 6 to 8 inches and 16 to 24 inches for even diffusion. Read the label for application depth directions and know the pest habits. For proper placement, you must know the pest habits and follow the product label instructions. Dosage depends on several factors. Different soil types require different rates, given the amount of pore space and amount of adsorption to clay and organic matter. Some pests, such as endoparasitic and cyst nematodes, require higher dosages than other pests. Rates also vary depending on what plants or crops Split Application for Pest Control will be planted. Perennial plants, trees, and vines require more fumigant than annual plants for which less control, and short-term effects are acceptable. Follow label directions. Performance data indicate label rates are effective. Applications above label rates are illegal and may damage the crop. Applications below label rates may not provide adequate pest control. Soil sealing is especially important in soil fumigation. Seal the soil immediately following fumigation, the sooner the better. The seal caps the soil surface, minimizing the amount of fumigant that escapes into the atmosphere. For effective pest control, keep the seal in place long enough to maintain a lethal gas concentration for the exposure period. It may be necessary to cover the area with a plastic tarp when using highly volatile chemicals, such as methyl bromide or chloropicrin, or when trying to control pests at or near the soil surface. Two other soil sealing methods are mechanical compaction (cultipacking, rolling, dragging) and light irrigation. If injection shank traces are present after treatment, disc them before sealing. For water seals, lightly water (to wet) the top inch or so of soil. Maintain that soil moisture throughout the exposure period. For optimum 10

11 effectiveness, seal the soil as the fumigation progresses. Exposure period varies depending on the pest organisms, the fumigant type and rate, soil moisture, and soil temperature. After the application and soil sealing, leave the soil undisturbed for the specified amount of time specified by the product label. Soil aeration may be necessary at the end of the fumigation exposure period to allow any fumigant in the soil to dissipate. Once the soil is properly aerated, growers can plant the crops or plants without concern for phytotoxicity. Application rate and depth, soil moisture, soil temperature, and sealing methods govern aeration times. Cool, moist soils tend to retain fumigant longer, requiring longer aeration periods. Cultivating the soil to the depth of fumigant application often aids aeration. Refer to the label to determine exposure times and aeration recommendations. Planting a test sample of seeds may be warranted in certain situations to ensure that no phytotoxic effects occur on highly susceptible plants. Phytotoxicity refers to plant injury and is a major concern when using soil fumigants. Most soil fumigants need to be applied weeks or months prior to planting because of potentially phytotoxic effects. Some plants or crops are very sensitive to small traces of soil fumigants, and phytotoxicity occurs when they are planted into soils where fumigant is still present. Read the fumigant label for specific precautions when planting certain plant varieties after fumigation. A minor concern is off-target movement (such as drift and runoff). Fumigant may escape through the soil surface and drift onto nearby susceptible plants. Rain or over irrigation may cause runoff. Pay close attention to what is planted on or is inhabiting areas near the application site. Test Your Knowledge Q. What pests may be controlled by soil fumigation? Why is it important to know about their life cycle and habits? A. Soil pests, such as plant parasitic nematodes, fungi, insect, bacteria, weeds and weed seeds. Understanding their habits gives you information for proper timing of fumigant application and to target the susceptible stage of the pest. Q. What factors are important in determining the placement of fumigants in soil? A. A combination of factors are important in determining where to place the fumigant in the soil. These include where the pest organism lives, soil temperature, dosage of fumigant, soil type, and vapor pressure of fumigant. Q. What influence does soil texture have on fumigant movement and availability? What type of soil requires more fumigant to attain a lethal dose? A. Soil texture influences the amount of soil pore space and the number of adsorption (binding) sites. Clay soils require more fumigant because these fine textured soils have many more binding sites and pore spaces than coarse textured soils. Q. What is the purpose of sealing the soil following fumigation? Must all soil fumigations be covered with a plastic tarp? A. Sealing the soil maintains a lethal gas concentration for the exposure period by minimizing the amount of fumigant that escapes into the atmosphere. Plastic tarps are used for methyl bromide and chlorpicrin soil fumigations, but soil compaction and water seals are used for other fumigants. * * * Q. What are the three fumigant formulations and what do they have in common? A. Liquefied gases, volatile liquids, and solids. They all convert to or volatilize into a gas when released into the soil. 11

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13 CHAPTER 3 Application Principles Learning Objectives After you complete your study of this chapter, you should be able to: Identify application techniques and equipment used to apply fumigants to soil. Application Techniques and Equipment Various types of soil fumigant application equipment are commercially available. Appropriate soil incorporation equipment and soil sealing equipment should follow or be attached to the fumigant equipment. Good fumigation equipment is expensive to build and maintain. Sometimes it is necessary to buy custom designed and built equipment for specific purposes. Because fumigants are highly corrosive, equipment manufacturers must construct equipment from materials tolerant or resistant to these chemicals. Proper care of fumigation equipment is essential. Clean application equipment immediately after use, and cover or coat all parts with a lightweight fuel oil before storing. Liquefied Gas Example: methyl bromide Above Ground Applications. Several devices are commercially available for applying liquefied gases to small areas, such as greenhouse growing media and nursery soil. Cover soil to be treated with plastic. Release fumigant through a plastic tube to an evaporation pan placed under sealed plastic. The fumigant flows under pressure from the container to the soil to be fumigated. Large cylinders require valves and pressure regulators to control the Aboveground Application onto an Evaporation Pan under a Tarp delivery of the gas to the evaporation pan. Use a separate pressurized cylinder of nitrogen to maintain a constant pressure to the fumigant cylinder, ensuring a uniform application rate. Equipment used with pressurized cylinders can be complex. The applicator must be certain that the application systems are designed to deliver and withstand the pressurized fumigant. Injection Applications. For overall field (broadcast) application of liquefied gases, such as methyl bromide, apply the fumigant using a tractor with sufficient horsepower to pull shanks (chisels) through the soil at the required depth and speed. For shallow applications (6 12 inches), mount shanks 12 inches apart on a tool bar connected directly to a machine that lays a plastic tarp. For deep applications (18 30 inches), mount shanks up to 66 inches apart, depending upon fumigation conditions. Fumigant delivery rates depend on equipment speed and flow rate of the chemical. The most commonly used machine to seal the soil with a plastic tarp consists of two discs that 13

14 open small furrows immediately outside the area to be treated. These discs connect to a device that unrolls polyethylene plastic over the treated area. Small press wheels insert the plastic into the open furrows. Closing discs seal the plastic by throwing soil back into the furrow. To treat a field on a broadcast basis, apply one strip as described above, then remove and replace one set of discs with an adhesive dispenser. Seal one side of the second plastic sheet using the adhesive to the first plastic sheet, and seal the other side of the second plastic sheet in the furrow made by the remaining discs. Repeat to fumigate and cover the entire field with plastic. The same type of fumigating equipment also is suitable for band applications (strip or row applications). For deep (18 30 inches) injections, sealing with a plastic tarp may not be necessary, depending on the target pests. Auger Applications. Use augers in perennial crops, such as deciduous fruits, nuts, vineyards, etc. Use them with either 1- or 1½-pound seamless cans or with large cylinders of gaseous fumigants. After the auger digs a hole approximately 5 feet deep, release the fumigant into the hole at the proper dosage, and then fill the hole and compact for a soil seal. Trench Application Volatile Liquids Examples: 1,3 dichloropropene, chloropicrin, metam sodium Trench Applications. To treat very small areas, such as ornamental planting beds, place the prescribed dosage of liquid fumigant in a small container. Pour the liquid into the bottom of a furrow 6 to 8 inches deep. Cover and seal trench. Form a water seal using a small amount of water. Handgun Applications. To treat small areas, such as experimental plots and nursery beds, use equipment with a holding tank connected to a hollow pointed base for penetrating the soil. A plunger device or drip device releases a known quantity of fumigant for each penetration. Shank (Chisel) Applications. This method is the one most commonly used to treat large-scale Hand-held Ground Injector areas, such as agricultural crops. Make field applications using tractors with sufficient horsepower to pull the shanks through the soil at the required depth and speed. Narrow knife-like shanks (such as 14

15 forward-swept shanks) inject fumigant. Metal delivery tubes attach to the trailing edges of the shanks. Delivery tubes release the fumigant in the bottom of the furrow made when pulling the shank through the soil. For broadcast applications, shank spacing usually equals the depth of injection. Maintain constant pressure to the metering pump, such as electrical or hydraulic pumps, power takeoff system (PTO), or ground-wheel drive. Regulate delivery rate using various combinations of pressure, nozzle orifice, shank spacing, and speed of travel, depending on the pressure system serving the metering pump. Shank equipment works for broadcast or band applications. For row applications, use equipment with either one or two shanks to treat only the soil where the crop will be planted. Seal the application with a plastic tarp or by mechanically compacting soil. If injection shank traces are present, disc soil to remove traces prior to sealing the soil. Sweep or Blade Applications. Attach fan shaped sweeps or blades equipped with evenly spaced fumigant outlets to the shanks and draw them through the soil. Seal the application with a plastic tarp or by mechanically compacting the soil. If blade shank traces are present, disc soil to remove traces prior to sealing the soil. Drench Application. Add the fumigant to water and drench the soil with this solution. This method is useful in nurseries, ornamental plantings, and orchards. Chemigation. To fumigate soil by chemigation, meter and inject a liquid fumigant into irrigation water. Fumigant chemigation is applied through several types of irrigation systems, most commonly center pivots. Equipment includes an injection pump and nurse tank system. Proper setup includes check valves between the injection pump and both the fumigant supply and the water source. Keep all screens and filters clean. Use as large a droplet as possible to avoid loss of fumigant through volatilization in the air. Chemigation often requires pre-irrigation to bring the field to the desired moisture level prior to fumigation. Moisture levels must be even throughout the field. Chemigation requires a high degree of attention to detail, an understanding of the equipment used, and constant monitoring during the application. Volatile Solids Basic Schematic of a Shank Applicator 15

16 Example: dazomet Broadcast Applications. Apply granules evenly over the soil and incorporate them, or inject the granules into the soil. For small scale applications, use a shaker and apply over the area. Incorporate granules into the soil and seal. For large-scale applications, use a granule spreader to broadcast treat and then incorporate, or use a fertilizer drill or granule distributor that will deliver the granules at the desired depth. Adjust application rate by changing the size of the opening from the hopper or by altering the speed of travel. Immediately after spreading, incorporate granules into soil to the proper depth using a rotary hoe or disc. Seal soil with a mechanical compactor. TEST YOUR KNOWLEDGE Q. Are liquefied gas fumigants applied by gravity flow or under pressure? A. Liquefied gas fumigants flow under pressure from the container to the soil to be fumigated. Q. Delivery rate of liquid fumigant applications is affected by what factor(s)? A. Delivery rate can be regulated by various combinations of metering pump pressure, nozzle orifice, shank spacing, and speed of travel. * * * 16

17 CHAPTER 4 Equipment Calibration Learning Objectives After you complete your study of this chapter, you should be able to: Describe the two basic methods used for calibrating fumigant application equipment. Know which calibration method should be used with specific types of fumigant application equipment. Learn how to calibrate fumigant application equipment to deliver desired rate of application. Calibration Methods Calibrate all application equipment to deliver the desired rate of chemical. All commercially constructed application equipment is designed to alter fumigant rates. Applicators use two basic methods for application equipment calibration. The first method measures the amount of fumigant applied over a known area. The second method collects a volume of fumigant for a specific time period and then measures the distance covered in the same time interval for a volume to area ratio. Application over a known area. This calibration method is useful for gravity flow and ground driven metering systems. Apply fumigant over a small, known area. Measure or weigh the amount of fumigant used over that area. Measurement may include determining the amount delivered by calculating the difference from the volume or weight at the start and the remaining volume or weight after the application to the known area, or simply by collecting the volume or weight delivered. Compute the amount per acre equivalent from the amount delivered (per small area). If necessary, adjust the equipment to more closely approach the desired amount and repeat the process. Follow equipment operation instructions to alter flow rate; methods differ among equipment. Repeat calibration several times until the equipment delivers the exact amount required per acre. To achieve the label application rate, use the following equation to determine the amount of Useful Conversions for Calibration 1 acre = 43,560 square feet (ft 2 ) 1 gallon (gal) = 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl oz) 1 gal = 3,785 milliliters (ml) 1 fl oz = ml 1 cubic foot of water = gal 1 acre inch of water = 27,156 gal 1 pound (lb) = 16 oz = grams (gm) 1 mile per hour (mph) = 88 feet per minute = feet per second (ft/sec) Circle circumference = 2 π r r = radius of circle π = Circle area = π r r r = radius of circle π = fumigant that you should apply over the calibration test area. 17

18 For example, to calibrate a shank applicator with a liquid fumigant, measure the effective swath width, W D R ft 2 = A orifice. Calculate flow rate per unit time. This is the common method for calibrating metering systems A = Amount of fumigant that should be delivered over calibration course. W = Width (feet) of the test swath. D R = Length (feet) of the test swath. = Desired amount (pounds or gallons) of fumigant per acre. 43,560 = Number of square feet (ft 2 ) per acre. let us say 8 feet wide with 7 shanks. The label rate for the application is 20 gallons of fumigant per acre. To calibrate, travel 100 feet with the application equipment and collect all the fumigant released from one outlet. (Make sure all nozzles deliver within 10% of each other to maintain a uniform application pattern. Replace nozzles that do not conform.) Multiply the amount collected by the number of shank outlets to get the total delivery rate of the equipment. How much fumigant should the equipment deliver from all the outlets if the equipment is calibrated at 20 gallons per acre? If the equipment delivered too much fumigant (more than 6.7 fl oz per nozzle), it is over applying. If the equipment delivered too little fumigant (less 8 ft 100 ft 20 gal ft 2 = gal gal 128 fl oz/gal = 47 fl oz for the system 47 fl oz 7 nozzles = 6.7 fl oz per nozzle than 6.7 fl oz per nozzle), it is under applying. Adjust the equipment until it delivers the proper amount of fumigant. Follow equipment manufacturer s instructions for changes. Adjustments may include altering pressure, application speed, or nozzle gal/ 800 ft 2 is equivalent to 2 gal/acre driven by PTO and electric or hydraulic pumps. For volatile liquids, measure fumigant flow rate for a specific time interval and then convert that measurement to an area basis dependent upon the application equipment speed. To alter the delivery rate, adjust the speed of travel, orifice size, shank spacing or pressure. For liquefied gases, such as methyl bromide, the method differs slightly since you cannot collect the gas. Weigh the gas cylinder first. Then release gas for a set time. Reweigh cylinders and calculate how much was released over the time interval. Calculate the distance the equipment travels for that same time interval. You now know the amount of fumigant applied per unit area. Convert to an acre basis. Adjust the in-line valve to tune the flow rate to the proper level for the proper delivery rate. To calibrate a shank applicator with a liquefied gas fumigant, measure the effective swath width of the shank row. For this example the width is 8 feet. The label rate is 350 pounds per acre. Weigh the cylinder. Release fumigant for 30 seconds. Reweigh the cylinder. Calculate the amount used in 30 seconds. 18

19 Determine the application equipment speed. Mark the start and finish of a 100-foot speed course. Time the equipment over the course, once each direction. Conduct the speed test in the application area with the equipment loaded and the shanks at application depth. Average the times determined across the speed course and convert to feet per second. Calculate the distance covered in 30 seconds. Now use the formula to determine the amount of fumigant that should be delivered on the 8-foot x 88-foot area (or in 30 seconds). If the equipment delivered too much fumigant (more than 5.66 lb in 30 seconds), it is over applying; reduce the flow rate. If the equipment delivered too little fumigant (less than 5.66 lb), it is under-applying; increase the flow rate. Adjust the flow rate until equipment delivers the proper rate in 30 seconds. Practice Problems Problem 1 A carrot grower wants to fumigate a field on a broadcast basis using a formulation of 1,3-D at 20 gallons per acre. The fumigant applicator is 12 feet wide and uses a ground driven pump to supply the chemical to the shanks, each spaced 12 inches apart. How much 1,3-D should be deposited by each shank during a calibration test over a swath 100 feet in length? Each shank covers a swath 1 foot wide (W = 1 ft) by 100 feet long (D = 100 ft). or Problem 2 A potato grower wants to broadcast a mixture of 1,3-D and chloropicrin at a rate of 27.5 gallons per acre. The fumigant will be applied 18 inches deep with a tractor-pto metering system, driven at a ground speed of 3.67 feet per second (2.5 mph). The V frame applicator treats an area 10.5 feet wide, with 7 shanks spaced 18 inches apart. How much soil fumigant should be deposited in a 30- second calibration trial? During the calibration test, the applicator will cover a swath 10.5 feet wide (W = 10.5 ft) by 110 feet long [110 ft = 3.67 ft/sec x 30 sec] (D = 110 ft) ft 110 ft 27.5 gal ft gal is for 7 shanks or 13.3 fl oz per shank Problem 3 A grower wants to apply a single shank in-row treatment of 1,3-D at a rate of 5 gallons per acre. The pesticide will be applied with a ground driven pump. The rows will be spaced 3 feet apart. How much of the fumigant will be deposited in a test row 50 feet long? 3 ft 50 ft 5 gal ft 2 = 0.73 gal = gal = 2.2 fl oz 1 ft 100 ft 20 gal ft fl oz per shank = gal Problem 4 The label rate for methyl bromide in a nursery operation is a broadcast rate of 400 pounds per acre for control of nematodes, weeds, and soilborne fungi. The effective swath width of the application is 10 feet wide. The application 19

20 equipment travels 2.2 feet per second (1.5 mph). How many pounds of methyl bromide must the fumigant applicator deliver every 30 seconds to achieve the 400 pounds per acre rate? The equipment will cover a swath 10 feet wide (W = 10 ft) by 66 feet long [66 ft = 2.2 ft/sec x 30 sec] (D = 66 ft). 10 ft 66 ft 400 lb ft 2 Chemigation - Fumigant application through irrigation requires great attention to calibration and operation details. Failure to calibrate accurately or to monitor the system continuously during the application can lead to costly mistakes. Poorly made applications may result in poor control or expensive and illegal applications that are above label rate. Check sprinkler system for proper operation and uniform water distribution. Check irrigation systems using catch cups to determine the speed of the irrigation system needed to provide at least 1 acreinch of water delivery. Once the timer is set to deliver 1 acre-inch of water, do not reset it before making the application. If the timer is reset for any reason, recalibrate the system to ensure an accurate level of water delivery. Check the injection pump and nurse tank system to ensure proper operation. Clean all screens and filters. Make sure check valves are in place between the injector pump and both the water source and the nurse tank. Determine the revolution time of the center pivot. Place a flag or marker at the end wheel and measure the distance traveled in a given time interval, such as 30 minutes. With a calculated circumference, calculate the revolution time. Once the revolution time (minutes per revolution) is known, calculate the injection rate and calibrate the injection pump for proper delivery. For example, the label rate for metam\ sodium is 50 gallons per acre. The center pivot is 1,320 feet to the end wheel, and the end gun covers an additional 40 feet (radius = 1360 ft), for a total of acres. When running at 45% on the timer, the center pivot applies 1 acre-inch of water. The pivot moves 346 feet in 2 hours at the end wheel. 20 = 6.1 lb First calculate how much metam sodium is needed for the job: End Wheel circumference: 8,294 ft Area: acres Product needed: 6,665 gal at fl oz/min 346 feet in 120 minutes Center Pivot Calculations Radius: 1360 ft = gallons x acre = 6,665 gallons acre Next, determine revolution time. It takes 2 hours (120 minutes) to travel 346 feet at the end wheel, so how long will it take to cover the entire circle? End wheel circumference = = ft = 8,294 ft. Set up a ratio calculation to determine end wheel revolution time: This means it takes 47.9 hours to cover the entire circle of acres, needing 6,665 gallons of 120 minutes =? minutes 346 ft 8294 ft 120 min 8294 ft = min 346 ft = 47.9 hours metam sodium. Next, calculate the amount of metam

21 sodium that must be injected, per minute, into the irrigation water to deliver 6,665 gallons per 2,876.5 minutes. A reduction in terms is all that is necessary: gallons to ounces or milliliters, depending upon how the injection system is set up. or To achieve an application rate of 50 gallons per acre in a pivot moving 173 feet per hour, inject 6665 gal min chemical at a rate of fluid ounces per minute fl oz min (2.3 gallons per minute). Problem 6 The center pivot irrigation system covers acres, with a radius of 1360 feet (1320 to the end wheel plus 40 feet for end gun). In one hour, the end wheel travels 210 feet. At 50% on the timer, it is applying 1 acre-inch of water. To achieve the label rate for nematode control in potatoes of 75 gallons per acre, how many milliliters of chemical need to be injected each minute? acres 75 gal per acre = 9,997.5 gal needed End wheel circumference = 2 π r = ft = 8,294 ft Revolution time of end wheel = 60 min 210 ft = 128 fl oz = fl oz/ gal min ml fl oz? min 8294 ft = ml/ min 60 min 8294 ft 210 ft gal min = min 128 fl oz ml = gal fl oz ml/min Test Your Knowledge Q. What are the two basic methods for calibrating fumigation application equipment? A. One method is to measure the amount of fumigant applied over a known area and the other method is to measure the distance covered in the same time interval for a volume to area ratio, i.e., calculating the flow rate per unit of time. Q. Which of these calibration methods is used for calibrating metering systems driven by PTO or hydraulic pumps? A. The method that calculates the flow rate per unit of time. Q. Why must this method be adjusted slightly for liquefied gases, such as methyl bromide? A. You can not collect the gas as it is released, so you must first weigh the cylinder containing the gas; release the gas; and then reweigh the cylinder. You can then calculate how much was released. * * * 21

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23 CHAPTER 5 Soil Fumigant Uses and Characteristics Learning Objectives After you complete your study of this unit, your should be able to: Describe the characteristics of the chemicals used as soil fumigants. Know placarding requirements for the transportation of methyl bromide and chloropicrin. Know the purpose and function of chlorpicrin in methyl bromide formulations. Methyl Bromide Methyl bromide is one of the most widely used soil fumigants. Methyl bromide is registered as a pre-plant treatment on a limited number of food crops as a soil fumigant. The food crops include strawberries, tomatoes, onions (dry bulb), peppers, cauliflower, broccoli, muskmelon hybrids (excludes watermelon), pineapple, eggplant, asparagus, lettuce, and Florida citrus. It also may be used on nursery and greenhouse soils, seed and transplant beds and turf, non-food crops, tobacco, and greenhouse tomatoes. Methyl bromide is a liquefied gas when it is stored under pressure in 1 or 1½-lb cans or in cylinders containing several hundred pounds of product. The compressed liquid readily vaporizes into gas when the cans or cylinders are opened in temperatures above 39 F. Methyl bromide is odorless, nonflammable, and generally not irritating to the eyes or skin during exposure but serious skin or eye injury may appear later. Since methyl bromide by itself has no irritating qualities to indicate its presence, many formulations contain chloropicrin as a warning agent. Chloropicrin has a strong odor and is very irritating to the eyes. All methyl bromide formulations registered for soil fumigation must contain chloropicrin. Mention of methyl bromide as a soil fumigant in this manual is with the understanding that chloropicrin is part of its formulation. When transporting any amount of methyl bromide, one should place a warning placard with the word POISON on the outside of the vehicle. Technically, placarding for methyl bromide is not required unless it is being transported in containers larger than 1 liter which includes cylinders or case lots of 1-pound or 1½-pound cans. Thus, when transporting only one or two individual 1-pound or 1½-pound cans of methyl bromide, placarding is not necessary. However, if transporting many individual small cans, each less than 1 liter, but the gross weight of all containers and products exceeds 1,000 pounds, then the vehicle does have to be placarded. To protect human life, if your vehicle is involved in an accident, it is strongly recommended that you take all necessary precautions, including placarding the vehicle, whenever you transport any amount of methyl bromide over public roads. Chloropicrin Chloropicrin has general biocidal activity. It is most active against soil fungi and insects with limited activity on weed seeds and nematodes. Chloropicrin is generally combined with other fumigants, such as methyl bromide and 1,3-D to increase the range of pests to be controlled and as a warning agent when added to odorless methyl bromide. When added to methyl bromide formulations at a concentration of 23

24 2% or less, it is considered to be only a warning agent. When used at concentrations greater than 2%, it is considered to be an active ingredient that augments the fumigant activity of methyl bromide. Chloropicrin is a yellowish liquid that vaporizes slowly when exposed to air at room temperature. It should not be used at temperatures below 40 F. Placarding requirements for transporting chloropicrin are the same as those described for methyl bromide (except that chloropicrin is not available in small cans). Metam-sodium Metam-sodium (sodium-n-methyldithiocarbamate) is also known as metam sodium and SMDC. It is a nonflammable volatile liquid formulated in a water-soluble solution and is sold under a variety of trade names, the most common of which is Vapam. It has been registered since 1954 for use as a preplant fumigant on a wide range of crops. It is active on some weeds, weed seeds, insects, nematodes, and soil-inhabiting fungi. When it is applied to soil, it decomposes in water to release the gas methyl isothiocyanate (MITC). Do not apply metam sodium within 3 feet of the drip line of desirable plants. Metam sodium is toxic to fish; do not apply it directly to water or allow runoff from treated areas to enter surface water. Also be aware that metam sodium is corrosive to brass and copper; use application equipment that is made of chemical-resistant materials. 1,3-D (1,3-Dichloropropene, Telone ) 1,3-D, sold as Telone, is an organochlorine chemical comprised of 1,3-dichloropropene and related chlorinated hydrocarbons. It is a volatile liquid and is sometimes formulated with chloropicrin to increase its efficacy against soil fungi, particularly Verticillium. It is registered for use on a wide range of field and vegetable crops, ornamentals, turf, tobacco, mint and some fruit crops. It has activity against nematodes and certain arthropods, specifically wireworms and symphylans. It is effective on some weeds or weed seeds and a few fungi at higher fumigant rates. It should not be used on heavy clay or muck soils. Dazomet Dazomet is used as a preplant fumigant to control germinating annual and perennial weeds and other pests on ornamental seed beds, forest seed beds, turf seed beds, and in potting soil. It is ineffective against cyst nematodes. Dazomet is available in three dry formulations: wettable powder, granule, and dust. Within 10 minutes after application, dazomet, in the presence of moisture, begins to break down. This chemical degradation results in the release of MITC, formaldehyde, hydrogen sulfide, and monomethylamine. These vapors interact to produce a potent killing agent. Soil ph does not affect this reaction. Dazomet is toxic to all living plants, therefore do not apply it within 3 4 feet of desired plants or within the dripline of trees or shrubs. The vapors are toxic to crops planted within three weeks after treatment, and exposure to vapors in the greenhouse can make workers ill. As with other fumigants, dazomet is toxic to fish; do not apply it directly to water or allow runoff from a treated area to enter surface water. Because it decomposes at high temperatures, dazomet should not be used when temperatures are above 90 F. Test Your Knowledge Q. Describe the characteristics of methyl bromide. A. Methyl bromide is a colorless, odorless, nonflammable gas that is a liquid when stored under pressure. 24

25 Q. What purpose does chloropicrin serve when it is formulated with methyl bromide? A. Chloropicrin has a strong odor, is very irritating to the eyes, and is used as a warning agent in methyl bromide formulations. When it is present in methyl bromide formulations at concentrations greater than 2% it is an active ingredient in addition to being a warning agent. Q. Are there any methyl bromide formulations registered for soil fumigation that do not contain chloropicrin? A. No, all methyl bromide formulations registered for soil fumigation must contain chloropicrin. Q. What must be done when transporting methyl bromide and chloropicrin? A. One should place a warning placard with the word POISON on the outside of the vehicle. Technically placarding is required when methyl bromide is transported in containers larger than one liter; however it is recommended to placard the vehicle when any amount of methyl bromide is transported. Q. Both metam sodium and dazomet decompose (break down) in the presence of water/moisture to release what gas? A. Both fumigants release methyl isothiocyanate (MITC) in the presence of water/moisture. * * * 25